1. Fossil Record: Fossils provide a direct record of life in the past. They show a progression of organisms over time, with older fossils generally simpler than newer ones. This supports the idea of gradual change and descent with modification. Furthermore, transitional fossils (like Archaeopteryx, which has features of both reptiles and birds) show evolutionary links between different groups.
2. Comparative Anatomy: The anatomical similarities between different species suggest common ancestry. For example, the bone structure of a human arm, a bat wing, a whale flipper, and a horse leg are remarkably similar, even though these structures serve different functions. This is explained by descent from a common ancestor with a similar skeletal structure.
3. DNA and Molecular Biology: The genetic code (DNA) is universal across all life forms, suggesting a common origin. Comparing DNA sequences between different species allows us to reconstruct evolutionary relationships and estimate how closely related species are. Moreover, the presence of homologous genes (genes with similar sequences in different species) further supports the idea of shared ancestry and evolutionary change.
